This invention relates to a picture signal processing device for processing picture signals for displaying e.g., enlarged, contracted or still pictures.
Nowadays, in a camera-integrated video tape recorder, referred to hereinafter as a camcorder, or a video tape recorder, a picture signal processing device having the function of an electronic zooming of forming picture signals of pixels shown in black circles from picture signals of pixels of white circles by enlarging processing of a horizontal line Z1, with an enlargement ratio of 2, as shown in FIG. 1A, the function of forming picture signals of pixels shown in black circles from picture signals of pixels of white circles by reducing processing of the horizontal line Z1, with a contraction ratio of 2, as shown in FIG. 2B, or the function of an electronic still of displaying a still picture by still picture processing, has become widespread.
In distinction from moving pictures, the enlarged picture and the still picture may be visually recognized easily on the pixel basis.
Thus, in connection with the above-described picture signal processing device, there is known a method of improving the picture quality by intra-field interpolation on detection of motion in a pixel-based picture, according to which, if, among pixels A, B, C and D of horizontal lines 1, 3, 5 and 7 of a first field and pixels E,F G and H of the horizontal lines 2, 4, 6 and 8 of a second field making up a frame with the first field, as shown in FIG. 2, the pixel G has been detected to be a moving pixel, picture signals of the pixel G of the second field are formed by intra-field interpolation from the pixels C and D respectively positioned above and below the pixel G and the picture signals of the pixels of the second field other than the pixel G, that is the pixels E and F, are formed by inter-field interpolation from the pixels A and B and from the pixels B and C of the first field disposed above and below the pixels E and F.
Meanwhile, motion detection in a picture is usually achieved based upon the picture signal level of detection scanning lines of the first field or the second field and the picture signal level of a scanning line neighboring to the detection scanning lines. If an edge component is present in the horizontal direction of picture signals, intra-field interpolation is performed based on mistaken motion detection in a picture even in case no motion has occurred in the picture, with the result that the picture quality by intra-field interpolation is deteriorated as compared to that by inter-field interpolation.
In addition, the picture processing device is in need of a memory for storing picture signals of 4-field picture signals, namely the picture signals of the first and second fields for detecting the motion of pictures, picture signals produced by the intra-field interpolation and picture signals of an enlarged picture, thus raising the cost.
On the other hand, if the motion of the picture of detected pixels is detected, since frame picture signals are generated based upon the first and second interpolated picture signals generated by intra-field interpolation in the first and second fields, as shown in FIGS. 3A and 3B, density fluctuations or picture signal level reversion is likely to occur on a boundary line of the interpolated portions of a picture represented by a frame.